Rotary metal cutting tool

Abstract: A rotary metal cutting tool comprises an elongate body (1) having at one end a shank (2) adapted to be clamped in a machine tool and a cutting head (3) provided at the other end of the body; at least one channel (4) provided in the head to receive a cutter blade (5); a recess (7) in the body (1); at least one clamping cotter (9) located in the recess (7) and serving to clamp the blade (5), by wedge action, against a seating surface (10) of the channel (4) by means of a clamping face (11) of the cotter engaging an opposite face (12) of the blade (5) to that engaging the seating surface (10); means (12) to urge the cotter into wedge clamping engagement with the blade (5); the recess and cotter each having at least one flat (13, 14) to prevent cotter rotation; and the clamping cotter (9) having a clamping surface (11) of extended length (16) terminating with the lower end face (17) of the cutting head (3).

Description: This invention relates to a rotary metal cutting tool according to the precharacterising portion of claim 1; see GB 2180177B. Such a tool comprises a body having at least one channel in which is clamped a replaceable cutter blade - typically a part-helical, carbide insert - and although this known tool has enjoyed considerable commercial success over a number of years, it is capable of further improvement. For instance in the machining of light alloy, swarf has been known to penetrate a tolerance gap between the tool body and cutter blade, frequently resulting in the blade being jammed in its recess even after removal of its clamping screw, due to the need to provide tolerance for the reasonably easy fitting of a replacement blade and the fact that, when using two axially spaced-apart clamping cotters for a blade of substantial axial length, the lower cotter was spaced above the lower end face of the tool head. In addition, in the fitting of a replacement blade, care had to be taken to ensure non-rotation of the securing cotter upon tightening of the cotter-locking screw, as any such rotation would tend to lift the adjacent blade from out of its seat. Consequently, a basic object of the present invention is to provide a rotary metal cutting tool of the aforementioned type but of further improved construction. According to the present invention there is provided a rotary metal cutting tool comprising; (i) an elongate body having at one end a shank adapted to be clamped in a machine tool and a cutting head provided at the other end of the body; (ii) at least one channel provided in the head to receive a cutter blade; (iii) a recess in the body; (iv) a clamping cotter located in the recess and serving to clamp the blade by wedge action, against a seating surface of the channel by means of a clamping face of the cotter engaging an opposite face of the blade to that engaging the seating surface; (v) means to urge the cotter into wedge clamping engagement with the blade; characterised in that: (vi) the recess and its cotter each hav flats to prevent cotter rotation; and (vii) the clamping cotter has a clamping surface that is extended so as to terminat with the lower end face of the cutting head. Thus, with the tool in accordance with the invention, firstly the tolerance gap of the prior art construction between the lower end face of the tool head and the blade is eliminated by extending the clamping face of the clamping cotter (or the lower clamping cotter if two clamping cotters per blade are employed) to the lower end face of the cutting head. Consequently, the potential for swarf accumulation in the tolerance gap is eliminated. Secondly, the flat between the or each clamping cotter and it or their recess(es) ensures that the cotter(s) cannot rotate upon tightening of the locking screw but on the contrary the clamping cotter in accordance with the invention positively pulls the blade into firm seating engagement with the seating surface of its channel. As indicated above, the axial length of the blade may require the use of two, axially spaced apart clamping cotters. Also, to avoid the need to balance the tool, the latter is preferably provided with multiple blades e.g. two 180° apart, three 120° apart, or four 90° apart. Although the blade(s) may be flat, preferably the blade is of helical form, e.g. of tungsten carbide, for which type of blade the cutting tool of the invention is particularly suitable. Preferably, two flats e.g. in the form of two parallel faces, are provided on the or each clamping cotter. Preferably, the flat(s) extends orthogonally or generally so, with respect to the clamping face of the cotter. One example of tool in accordance with the invention is shown in the accompanying drawings, in which:- Figure 1 is a side elevation of a tool in accordance with the invention; Figure 2 is a view in the direction of arrow A; and Figures 3, 4, 5 and 6, are side, end, opposite side and plan views respectively of one of the lower clamping cotters of Figures 1 and 2. In the drawings, the rotary metal cutting tool comprises an elongate body 1 having at one end a shank 2 adapted to be clamped in a machine tool and at the other end a cutting head 3. Three channels 4 are provided 120° in the head 3 each to receive a replaceable, tungsten carbide cutter blade 5 twisted to helical form. The body member is also provided with two recesses 6, 7 intersecting each channel 4. A lower clamping cotter 9 is located in the recess 7 and a second upper clamping cotter 8 is located in the recess 6. The clamping cotters 8, 9 serve to clamp the associated blade 5, by wedge action, against a seating surface 10 of each channel 4 by means of a clamping face 11 of each cotter engaging an opposite face 12 of the associated blade 5 to that engaging the seating surface 10. Each clamping cotter 8, 9 is provided with a through hole 13 to receive a recessed hexagon head screw 14 to urge each cotter 8, 9 into wedge clamping engagement with the associated blade 5. The recess 6, 7 and the clamping cotters 8, 9 each have respectively a flat 15, 15A; 16, 16A to prevent cotter rotation during tightening of the associated screw 14. The lower clamping cotter 7, i.e. nearer to the lower end face of the cutting head 3, has a clamping surface 18 of extended length terminating at 19 so as to be contiguous, or generally so, with the end face of the cutting head. Other than an extension 19 of its clamping surface 11, the first, upper clamping cotters 8 are identical to the cotters 9.

Claims: A rotary metal cutting tool comprising: (i) an elongate body (1) having at one end a shank (2) adapted to be clamped in a machine tool and a cutting head (3) provided at the other end of the body; (ii) at least one channel (4) provided in the head (3) to receive a cutter blade (5); (iii) a recess (7) in the body; (iv) a clamping cotter (9) located in the recess (7) and serving to clamp the blade (5) by wedge action, against a seating surface (10) of the channel (5) by means of a clamping face (11) of the cotter (9) engaging an opposite face (12) of the blade (5) to that engaging the seating surface (10); (v) means (13, 14) to urge the cotter (9) into wedge clamping engagement with the blade (5); characterised in that: (vi) the recess (7) and its cotter (9) each have flats (15, 15A; 16, 16A) to prevent cotter rotation; and (vii) the clamping cotter (9) has a clamping surface (18) that is extended so as to terminate with the lower end face (17) of the cutting head (3). A tool as claimed in Claim 1, wherein the or each blade (5) has an axial length such that a second, clamping cotter (8), axially spaced from the cotter (9), is provided. A tool as claimed in Claim 1 or Claim 2, wherein two blades (5) are provided 180° apart. A tool as claimed in Claim 1 or Claim 2, wherein three blades (5) are provided 120° apart. A tool as claimed in Claim 1 or Claim 2, wherein four blades (5) are provided 90° apart. A tool as claimed in any preceding Claim, wherein two flats (16, 16A) are provided on opposite sides of the second clamping cotter (8). A tool as claimed in Claim 6, wherein the two flats (16, 16A) are in the form of parallel faces. A tool as claimed in any one of Claims 1 to 5, wherein the flats (16, 16A) of the cotter (9) extend orthogonally or generally so, with respect to each other.

Inventors: REYNOLDS PAUL ADRIAN, REYNOLDS, PAUL ADRIAN
Applicants: HYDRA TOOLS INT PLC, HYDRA TOOLS INTERNATIONAL LIMITED
Application year: 1994
Main classification: B23C5
IPC codes: B23C5